China's National Development and Reform Commission (NDRC) has been investigating premium brands such as Audi and Mercedes-Benz for allegedly anti-competitive acts, including price fixing.

The government's anti-trust campaign "could lead to downward adjustment in premium pricing, which helps provide solid foundation for premium vehicle penetration to further increase in China in the next decade," IHS said in a statement.

The Americas

Another demand bright spot will be in North America, IHS said, forecasting the combined U.S., Mexico and Canada sales will rise 2.5 percent on-year to 20 million units, with 16.9 million of those in the U.S.

"With a strong exit to 2014, and gasoline prices currently plunging, [U.S.] consumers may feel even more positive throughout 2015," IHS said.

In South America, however, there isn't likely to be much recovery from 2014's 10 percent on-year sales drop, IHS said.

"With politics impairing Argentina and Venezuela, and the economic climate weighing down markets like Brazil, Chile and Peru, … it may take a few years for demand to recover to previous highs," IHS said.

Europe to weigh

Europe is also likely to weigh on global auto sales, with an expected 3 percent increase in Western Europe's auto sales, offset by concerns over Russia, IHS said.

"As the Russian economy slumps into a deep recession in 2015, its negative impact on the euro zone and surrounding countries could be large enough to offset the consumer benefit from falling fuel prices," IHS said. It expects the recent volatility in the Russian ruble has pushed up imported car prices by over 20 percent, while domestically produced vehicles may also see double-digit price hikes, it said.

IHS forecasts Russian car sales this year will fall 27 percent on-year to 1.8 million units.